Liquid crystal display device and display apparatus

ABSTRACT

Disclosed is a liquid crystal display (LCD) device. The LCD device includes a first substrate and a second substrate facing each other, a liquid crystal layer between the first substrate and the second substrate, an alignment layer on at least one of the first and second substrates for alignment of liquid crystals in the liquid crystal layer, and a sealant in an edge area of each of the first and second substrates to bond the first substrate to the second substrate, the sealant including a diene compound.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 14/875,510 filed on Oct. 5, 2015, which claims the benefit ofRepublic of Korea Patent Application No. 10-2014-0177865 filed on Dec.10, 2014, all of which are hereby incorporated by reference as if fullyset forth herein.

BACKGROUND

Field of the Invention

The present invention relates to a liquid crystal display (LCD) deviceand a display apparatus, and more particularly, to a sealant for bondinga lower substrate to an upper substrate.

Discussion of the Related Art

LCD devices include a lower substrate, an upper substrate, and a liquidcrystal layer formed therebetween, wherein an alignment state of theliquid crystal layer is changed by an electric field applied thereto,and thus, a transmittance of light is adjusted, thereby displaying animage.

Hereinafter, a related art LCD device will be described with referenceto the drawing.

FIG. 1 is a schematic cross-sectional view of a related art LCD device.

As seen in FIG. 1, the related art LCD device includes an uppersubstrate 10, a lower substrate 20, a liquid crystal layer 30, and asealant 40.

Although not shown in detail, a black matrix and a color filter areformed on the upper substrate 10, and a thin film transistor (TFT) and apixel electrode are formed on the lower substrate 20.

The liquid crystal layer 30 is formed between the upper substrate 10 andthe lower substrate 20. Alignment layers 12 and 22 are formed on asurface contacting the liquid crystal layer 30, for an initial alignmentof the liquid crystal layer 30. That is, an upper alignment layer 12 isformed on a bottom surface of the upper substrate 10, and a loweralignment layer 22 is formed on a top surface of the lower substrate 20.

The sealant 40 is formed on an edge area between the upper substrate 10and the lower substrate 20. The sealant 40 bonds the upper substrate 10to the lower substrate 20 and prevents the liquid crystal layer 30 frombeing leaked to the outside. Therefore, the sealant 40 includes, as amain component, an adhesive component for bonding the upper substrate 10to the lower substrate 20.

Recently, an attempt to newly design LCD devices is being continuouslymade for satisfying various demands of consumers, and to this end, anattempt to decrease bezel widths of the LCD devices is made. If a bezelwidth of an LCD device is reduced, a display surface where an image isdisplayed is enlarged. In order to reduce a bezel width, an area wherethe sealant 40 contacts the alignment layers 12 and 22 is enlarged. Thiswill be described below in detail.

When a bezel width of the LCD device is large, an interval or a distancebetween an end of the upper substrate 10 and an end of the upperalignment layer 12 may be broadened, and thus, the sealant 40 may beformed not to contact the upper alignment layer 12. Also, an interval ora distance between an end of the lower substrate 20 and an end of thelower alignment layer 22 may be broadened, and thus, the sealant 40 maybe formed not to contact the lower alignment layer 22.

On the other hand, when a bezel width of the LCD device is small, theinterval or a distance between the end of the upper substrate 10 and theend of the upper alignment layer 12 should be reduced, and for thisreason, it is difficult to form the sealant 40 so as not to contact theupper alignment layer 12. Also, since the interval or the distancebetween the end of the lower substrate 20 and the end of the loweralignment layer 22 should be reduced, it is difficult to form thesealant 40 so as not to contact the lower alignment layer 22. Therefore,as illustrated, the sealant 40 contacts the alignment layers 12 and 22.

However, an adhesive force between the upper substrate 10 and the lowersubstrate 20 is more reduced in a case, where the sealant 40 is formedto contact the alignment layers 12 and 22 for reducing a bezel width ofthe LCD device, than a case where the sealant 40 is formed not tocontact the alignment layers 12 and 22.

SUMMARY

Accordingly, the present invention is directed to provide a liquidcrystal display (LCD) device and a display apparatus that substantiallyobviate one or more problems due to limitations and disadvantages of therelated art.

When a sealant contacts an alignment layer, an adhesive force between anupper substrate and a lower substrate is reduced. Therefore, in order toenhance the adhesive force between the upper substrate and the lowersubstrate, it can be proposed to form the sealant not to contact thealignment layer or enhance bonding force between the sealant and thealignment layer.

Since the method of forming the sealant not to contact the alignmentlayer causes an increase in a bezel width of the LCD device, it isdifficult to satisfy the recent demands of consumers. Therefore, thepresent invention provides a method that enhances a bonding forcebetween a sealant and an alignment layer so as to reduce a bezel widthof the LCD device and enhance an adhesive force between an uppersubstrate and a lower substrate.

Additional advantages and features of the invention will be set forth inpart in the description which follows and in part will become apparentto those having ordinary skill in the art upon examination of thefollowing or may be learned from practice of the invention. Theobjectives and other advantages of the invention may be realized andattained by the structure particularly pointed out in the writtendescription and claims hereof as well as the appended drawings.

To achieve these and other advantages and in accordance with the purposeof the invention, as embodied and broadly described herein, there isprovided a liquid crystal display (LCD) device including: a firstsubstrate and a second substrate facing each other; a liquid crystallayer between the first substrate and the second substrate; an alignmentlayer on at least one of the first and second substrates for alignmentof liquid crystals in the liquid crystal layer; and a sealant in an edgearea of each of the first and second substrates to bond the firstsubstrate to the second substrate, the sealant including a dienecompound.

The diene compound may include a compound represented by ChemicalFormula 1:

where R₁, R₂, and R₃ are independently one among hydrogen, a halogenatom, a phenyl group, an alkyl group of C₁˜C₉, an alkoxy group of C₁˜C₉,a vinyl group of C₂˜C₄, and an acetyl group of C₂˜C₄, and R₄ is oneamong a phenyl group, an alkyl group of C₁˜C₉, an alkoxy group of C₁˜C₉,a vinyl group of C₂˜C₄, and an acetyl group of C₂˜C₄.

The alignment layer may include a compound represented by ChemicalFormula 2:

where R₅ is one among hydrogen, halogen atom, a phenyl group, an alkylgroup of C₁˜C₉, an alkoxy group of C₁˜C₉, a vinyl group of C₂˜C₄, and anacetyl group of C₂˜C₄, and R₆ and R₇ are independently one amonghydrogen and an alkyl group of C₁˜C₆.

The sealant may contact the alignment layer, and a contact surfacebetween the sealant and the alignment layer may include a compoundrepresented by Chemical Formula 3:

where R₁, R₂, R₃, and R₅ are independently one among hydrogen, a halogenatom, a phenyl group, an alkyl group of C₁˜C₉, an alkoxy group of C₁˜C₉,a vinyl group of C₂˜C₄, and an acetyl group of C₂˜C₄, and R₄ is oneamong a phenyl group, an alkyl group of C₁˜C₉, an alkoxy group of C₁˜C₉,a vinyl group of C₂˜C₄, and an acetyl group of C₂˜C₄, and R₆ and R₇ areindependently one among hydrogen and an alkyl group of C₁˜C₆.

The diene compound may be chemically bonded to the alignment layer byultraviolet (UV) rays.

A chemical bond of a compound for the alignment layer may not be brokenwithin a wavelength range of the UV rays.

An alignment direction of a compound for the alignment layer may bedetermined by UV rays having a wavelength range which does not overlap awavelength range of the UV rays involved in the diene compound chemicalbonding to the alignment layer.

The sealant may further include an epoxy resin, and the alignment layermay include amic acid.

The sealant may contact the alignment layer, and a contact surfacebetween the sealant and the alignment layer may include a COO bond by areaction of the epoxy resin with a carboxylic group (COOH) of the amicacid.

In another aspect of the present invention, there is provided a displayapparatus including: a first substrate and a second substrate facingeach other; an alignment layer on at least one of the first and secondsubstrates; and a sealant configured to bond the first substrate to thesecond substrate, wherein the sealant includes a compound that reactswith the alignment layer within a wavelength range where a chemical bondincluded in the alignment layer is maintained, for enhancing adhesivebonding force between the sealant and the alignment layer.

The wavelength range where the chemical bond included in the alignmentlayer is maintained may be 300 nm to 420 nm.

The alignment layer may include a maleimide functional group.

The sealant may be chemically bonded to the maleimide functional group.

The sealant may include a diene compound.

The sealant may include a compound represented by Chemical Formula 1:

where R₁, R₂, and R₃ are independently one among hydrogen, a halogenatom, a phenyl group, an alkyl group of C₁˜C₉, an alkoxy group of C₁˜C₉,a vinyl group of C₂˜C₄, and an acetyl group of C₂˜C₄, and R₄ is oneamong a phenyl group, an alkyl group of C₁˜C₉, an alkoxy group of C₁˜C₉,a vinyl group of C₂˜C₄, and an acetyl group of C₂˜C₄.

The alignment layer may include a compound represented by ChemicalFormula 2:

where R₅ is one among hydrogen, a halogen atom, a phenyl group, an alkylgroup of C₁˜C₉, an alkoxy group of C₁˜C₉, a vinyl group of C₂˜C₄, and anacetyl group of C₂˜C₄, and R₆ and R₇ are independently one amonghydrogen and an alkyl group of C₁˜C₆.

The sealant may contact the alignment layer, and a contact surfacebetween the sealant and the alignment layer may include a compoundrepresented by Chemical Formula 3:

where R₁, R₂, R₃, and R₅ are independently one among hydrogen, a halogenatom, a phenyl group, an alkyl group of C₁˜C₉, an alkoxy group of C₁˜C₉,a vinyl group of C₂˜C₄, and an acetyl group of C₂˜C₄, and R₄ is oneamong a phenyl group, an alkyl group of C₁˜C₉, an alkoxy group of C₁˜C₉,a vinyl group of C₂˜C₄, and an acetyl group of C₂˜C₄, and R₆ and R₇ areindependently one among hydrogen and an alkyl group of C₁˜C₆.

The sealant may further include an epoxy resin, and the alignment layermay include amic acid.

The sealant may contact the alignment layer, and a contact surfacebetween the sealant and the alignment layer may include a COO bond by areaction of the epoxy resin with a carboxylic group (COOH) of the amicacid.

A bezel width of the display apparatus having the compound of thesealant may be relatively reduced compared to a bezel width of a displayapparatus without the compound of the sealant.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiments of the invention andtogether with the description serve to explain the principle of theinvention. In the drawings:

FIG. 1 is a schematic cross-sectional view of a related art LCD device;

FIG. 2 illustrates a chemical bond form between a sealant and analignment layer according to an embodiment of the present invention; and

FIG. 3 is a schematic cross-sectional view of an LCD device according toan embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the exemplary embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts.

Advantages and features of the present invention, and implementationmethods thereof will be clarified through following embodimentsdescribed with reference to the accompanying drawings. The presentinvention may, however, be embodied in different forms and should not beconstrued as limited to the embodiments set forth herein. Rather, theseembodiments are provided so that this disclosure will be thorough andcomplete, and will fully convey the scope of the present invention tothose skilled in the art. Further, the present invention is only definedby scopes of claims.

A shape, a size, a ratio, an angle, and a number disclosed in thedrawings for describing embodiments of the present invention are merelyan example, and thus, the present invention is not limited to theillustrated details. Like reference numerals refer to like elementsthroughout. In the following description, when the detailed descriptionof the relevant known function or configuration is determined tounnecessarily obscure the important point of the present invention, thedetailed description will be omitted. In a case where ‘comprise’,‘have’, and ‘include’ described in the present specification are used,another part may be added unless ‘only˜’ is used. The terms of asingular form may include plural forms unless referred to the contrary.

In construing an element, the element is construed as including an errorrange although there is no explicit description.

In describing a position relationship, for example, when a positionrelation between two parts is described as ‘on˜’, ‘over˜’, ‘under˜’, and‘next˜’, one or more other parts may be disposed between the two partsunless ‘just’ or ‘direct’ is used.

In describing a time relationship, for example, when the temporal orderis described as ‘after˜’, ‘subsequent˜’, ‘next˜’, and ‘before˜’, a casewhich is not continuous may be included unless ‘just’ or ‘direct’ isused.

It will be understood that, although the terms “first”, “second”, etc.may be used herein to describe various elements, these elements shouldnot be limited by these terms. These terms are only used to distinguishone element from another. For example, a first element could be termed asecond element, and, similarly, a second element could be termed a firstelement, without departing from the scope of the present invention.

Features of various embodiments of the present invention may bepartially or overall coupled to or combined with each other, and may bevariously inter-operated with each other and driven technically as thoseskilled in the art can sufficiently understand. The embodiments of thepresent invention may be carried out independently from each other, ormay be carried out together in co-dependent relationship.

Hereinafter, exemplary embodiments of the present invention will bedescribed in detail with reference to the accompanying drawings.

The inventors have researched on a method that creates a chemical bondbetween a sealant and an alignment layer on a contact surface of thesealant and the alignment layer so as to enhance a bonding force betweenthe sealant and the alignment layer, thereby completing the invention.This will be described below in detail.

Since the sealant is finished through a hardening process after acoating process of the sealant, a bonding force between the sealant andthe alignment layer is enhanced by applying a method that creates achemical bond between the sealant and the alignment layer in a processof hardening the sealant. In other words, since the sealant undergoes anultraviolet (UV) hardening process and a heat hardening process, thepresent invention applies a method that creates the chemical bondbetween the sealant and the alignment layer in the process of hardeningthe sealant so as to enhance the bonding force between the sealant andthe alignment layer. The alignment layer is formed of polyimide that isproduced by polymerizing a monomer, but since a monomer is notcompletely polymerized into polyimide generally, an unpolymerizedintermediate product remains on a surface of the alignment layer.Therefore, when a component capable of being chemically bonded to theintermediate product is added into the sealant, the intermediate productof the alignment layer is chemically bonded to the component added intothe sealant, and thus, the bonding force between the sealant and thealignment layer is enhanced.

Amic acid is produced as an intermediate product in a process ofproducing polyimide that is a component of the alignment layer.Therefore, the alignment layer includes polyimide and amic acid. Amicacid contains a carboxylic group (COOH), and the inventors haverecognized that the carboxylic group (COOH) is bonded to an epoxy groupby irradiating UV rays in a process of hardening the sealant. Therefore,when an epoxy group is added into the sealant and the sealant ishardened by the UV rays, the bonding force between the sealant and thealignment layer is enhanced by a chemical bond between the epoxy groupincluded in the sealant and a carboxylic group (COOH) included in thealignment layer.

FIG. 2 illustrates a chemical bond form between a sealant and analignment layer according to an embodiment of the present invention. Asseen in FIG. 2, when an epoxy group is added into a sealant, acarboxylic group (COOH) of amic acid included in an alignment layer ischemically bonded to the epoxy group included in the sealant byirradiating UV rays in a process of hardening the sealant, and thus, achemical bond that is a COO bond is created on a contact surface of thesealant and the alignment layer. Therefore, when the epoxy group isadded into the sealant and a UV ray irradiating process is performed forthe sealant, a COO bond (an ester bond) that is a chemical bond betweenthe sealant and the alignment layer is created, thereby enhancing abonding force between the sealant and the alignment layer. Since thebonding force between the sealant and the alignment layer is enhanced,the sealant and the alignment layer may be formed to contact each other,and a bezel width of the device is reduced.

Moreover, the inventors have additionally confirmed that a component ofan intermediate product remaining in an alignment layer is changeddepending on a process of forming the alignment layer. That is, amicacid remains in the alignment layer when the alignment layer is formedby a rubbing alignment process. When the alignment layer is formed by anUV alignment process, an imide rate increases, and thus, carboxylicgroups (COOH) of amic acid remaining in the alignment layer are reduced.For this reason, even when the epoxy group is added into the sealant asdescribed above, the inventors have confirmed that a bonding forcebetween the sealant and the alignment layer is not enhanced. Therefore,the inventors have additionally researched on a component remaining inthe alignment layer when the alignment layer is formed by the UValignment process.

When an UV alignment layer is applied, an imide rate of polyimide thatis a component of an alignment layer increases for solving a problem ofimage sticking. When an imide rate of polyimide increases, as describedabove, amic acids remaining in the alignment layer are reduced. Instead,the inventors have confirmed that when UV rays are irradiated onpolyimide for an UV alignment, a bond in polyimide is broken, and thus,a maleimide functional group exists on a surface of the alignment layer.Therefore, a component capable of being chemically bonded to themaleimide functional group may be added into the sealant so as toenhance a bonding force between the sealant and the alignment layer.

The inventors have researched on a component that is capable of beingchemically bonded to a maleimide functional group and is able to beadded into a sealant, and as a result of the research, the inventorshave confirmed that a diene compound is chemically bonded to the amaleimide functional group and is applied as a component of the sealant.Also, the inventors have confirmed that a diene compound represented bythe following Chemical Formula 1 is suitable as the component of thesealant, and thus have completed the invention.

In Chemical Formula 1, R₁, R₂, and R₃ are independently one amonghydrogen, a halogen atom, a phenyl group, an alkyl group of C₁˜C₉, analkoxy group of C₁˜C₉, a vinyl group of C₂˜C₄, and an acetyl group ofC₂˜C₄, and R₄ is one among a phenyl group, an alkyl group of C₁˜C₉, analkoxy group of C₁˜C₉, a vinyl group of C₂˜C₄, and an acetyl group ofC₂˜C₄.

The diene compound represented by Chemical Formula 1 may be chemicallybonded to a maleimide functional group represented by the followingChemical Formula 2 through a reaction represented by the followingReaction Chemical Formula 1.

In Chemical Formula 2, R₅ is one among hydrogen, a halogen atom, aphenyl group, an alkyl group of C₁˜C₉, an alkoxy group of C₁˜C₉, a vinylgroup of C₂˜C₄, and an acetyl group of C₂˜C₄, and R₆ and R₇ areindependently one among hydrogen and an alkyl group of C₁˜C₆.

As seen in Reaction Formula 1, a compound represented by ChemicalFormula 4 may be produced by irradiating an UV ray on the diene compoundrepresented by Chemical Formula 1 for hardening a sealant, and acompound represented by Chemical Formula 3 may be produced by chemicallybonding the compound represented by Chemical Formula 4 to the maleimidefunctional group represented by Chemical Formula 2. Therefore, acompound represented by Chemical Formula 3 may exist on a contactsurface between the sealant and an alignment layer, and thus, a bondingforce between the sealant and the alignment layer is enhanced.

In Chemical Formula 3, R₁, R₂, R₃, and R₅ are independently one amonghydrogen, a halogen atom, a phenyl group, an alkyl group of C₁˜C₉, analkoxy group of C₁˜C₉, a vinyl group of C₂˜C₄, and an acetyl group ofC₂˜C₄, and R₄ is one among a phenyl group, an alkyl group of C₁˜C₉, analkoxy group of C₁˜C₉, a vinyl group of C₂˜C₄, and an acetyl group ofC₂˜C₄, and R₆ and R₇ are independently one among hydrogen and an alkylgroup of C₁˜C₆.

A material cannot be considered to be suitable as a sealant component byonly the reason of being chemically bonded to the alignment layer. Thisis because an alignment direction of a completed UV alignment layer isin disorder again, if a polyimide bond of the completed UV alignmentlayer is broken by the UV rays which is irradiated on the diene compoundrepresented by Chemical Formula 1 in Reaction Formula 1 for hardeningthe sealant.

Therefore, a material capable of creating a chemical bond within awavelength range where the polyimide bond included in the alignmentlayer is not broken may be applied as a component of the sealant, andthus, the inventors have completed the invention after finallyconfirming that the diene compound represented by Chemical Formula 1satisfies such a condition.

That is, a photo-alignment process or UV alignment process for polyimidewhich is the alignment layer may be performed by irradiating UV rayshaving a wavelength of 240 nm to 254 nm, but the compound represented byChemical Formula 4 in Reaction Formula 1 may be produced by irradiatingUV rays having a wavelength of 300 nm to 420 nm on the diene compoundincluded in the sealant represented by Chemical Formula 1. In otherwords, since polyimide which is a component of the alignment layercannot react within a wavelength of 300 nm to 420 nm, the alignmentlayer is prevented from being damaged by the UV ray irradiation.

FIG. 3 is a schematic cross-sectional view of a LCD device according toan embodiment of the present invention.

As seen in FIG. 3, the LCD device according to an embodiment of thepresent invention may include a first substrate 100, a second substrate200, a liquid crystal layer 300, and a sealant 400.

The first substrate 100 may be an upper substrate of the LCD device. Indetail, a light shielding pattern 120, a color filter 140, an overcoatlayer 160, and a first alignment layer 180 may be formed on the firstsubstrate 100, in more detail, on a bottom of the first substrate 100facing the second substrate 200.

The light shielding pattern 120 may be formed on the bottom of the firstsubstrate 100. The light shielding pattern 120 prevents light from beingleaked to an area other than a pixel area. The light shielding pattern120 may be formed in a matrix structure, and an area between adjacentlight shielding patterns 120 may constitute the pixel area.

The color filter 140 may be formed on the bottom of the first substrate100. The color filter 140 may be formed in the area between the adjacentlight shielding patterns 120. The color filter 140 may include a red (R)color filter, a green (G) color filter, and a blue (B) color filterwhich are respectively provided in a plurality of pixels.

The overcoat layer 160 may be formed on a bottom of each of the lightshielding pattern 120 and the color filter 140. The overcoat layer 160may planarize the bottom surface of the first substrate 100.

The first alignment layer 180 may be formed on a bottom surface of theovercoat layer 160 to determine an alignment direction of liquidcrystals in the liquid crystal layer 300. The first alignment layer 180may include polyimide. The first alignment layer 180 may be formed by arubbing alignment process or a UV alignment process.

When the first alignment layer 180 is formed by the rubbing alignmentprocess, as described above, the first alignment layer 180 may includeamic acid which is an intermediate product, and thus, a COOH group ofamic acid may be included in the bottom surface of the first alignmentlayer 180.

When the first alignment layer 180 is formed by the UV alignmentprocess, as described above, a content of amic acid which is theintermediate product may be reduced. However, a chemical bond inpolyimide may be broken by UV ray irradiation, and thus, the maleimidefunctional group represented by Chemical Formula 2 may be included inthe bottom surface of the first alignment layer 180.

The second substrate 200 may be a lower substrate of the LCD device. Athin film transistor (TFT) T, a pixel electrode 250, a common electrode260, and a second alignment layer 280 may be formed on the secondsubstrate 200, in more detail, on a top surface of the second substrate200 facing the first substrate 100.

In more detail, a gate electrode G, a gate insulation layer 220, anactive layer A, a source electrode S, a drain electrode D, a passivationlayer 230, a planarization layer 240, a pixel electrode 250, a commonelectrode 260, and a second alignment layer 280 may be formed on the topsurface of the second substrate 200.

The gate electrode G may be formed on the second substrate 200.

The gate insulation layer 220 may be formed on the gate electrode G toinsulate the gate electrode G from the active layer A.

The active layer A may be formed on the gate insulation layer 220.

The source electrode S may be formed on one side of the active layer A,and the drain electrode D may be formed on the other side of the activelayer A.

The passivation layer 230 may be formed on the source electrode S andthe drain electrode D to protect the source electrode S and the drainelectrode D.

The planarization layer 240 may be formed on the passivation layer 230to planarize the top surface of the second substrate 200.

The TFT T may include the gate electrode G, the active layer A, thesource electrode S, and the drain electrode D. In FIG. 3, a TFT having abottom gate structure where the gate electrode G is disposed under theactive layer A is illustrated, but the TFT T according to an embodimentof the present invention may include a top gate structure where the gateelectrode G is disposed over the active layer A. In addition, astructure of the TFT T according to an embodiment of the presentinvention may be changed to various structures, known to those skilledin the art, such as a double gate (or a dual gate) structure and/or thelike.

The pixel electrode 250 and the common electrode 260 may be formed onthe planarization layer 240. The pixel electrode 250 may be connected tothe drain electrode D of the TFT T through a contact hole which isformed in the planarization layer 240 and the passivation layer 230. Thecommon electrode 260 may be arranged in parallel with the pixelelectrode 250, and thus, an alignment state of the liquid crystal layer300 may be adjusted by a horizontal electric field between the commonelectrode 260 and the pixel electrode 250.

In FIG. 3, the pixel electrode 250 and the common electrode 260 areillustrated as being formed on the same layer, but are not limitedthereto. As another example, the pixel electrode 250 and the commonelectrode 260 may be formed on different layers.

The LCD device according to an embodiment of the present invention maybe applied to various modes, known to those skilled in the art, such asa twisted nematic (TN) mode and a vertical alignment (VA) mode where thealignment state of the liquid crystal layer 300 is adjusted by avertical electric field, in addition to an in-plane switching (IPS) modeand a fringe field switching (FFS) mode where the alignment state of theliquid crystal layer 300 is adjusted by a horizontal electric field.Therefore, positions and shapes where the common electrode 260 and thepixel electrode 250 are formed may be variously changed. For example, inthe FFS mode, the common electrode 260 may be formed between thepassivation layer 230 and the planarization layer 240. In the TN mode,the common electrode 260 may be formed at a position of the overcoatlayer 160 on the first substrate 100, and the overcoat layer 160 may beomitted.

The second alignment layer 280 may be formed on the pixel electrode 250and the common electrode 260 to determine an initial alignment directionof liquid crystals in the liquid crystal layer 300. An alignmentdirection of the second alignment layer 280 may be vertical to that ofthe first alignment layer 180, but is not limited thereto.

Similarly to the above-described first alignment layer 180, the secondalignment layer 280 may include polyimide and may be formed by therubbing alignment process or the UV alignment process. Therefore, a COOHgroup of amic acid may be included in a top surface of the secondalignment layer 280, and in addition to the COOH group, the maleimidefunctional group represented by Chemical Formula 2 may be included inthe top surface of the second alignment layer 280.

The liquid crystal layer 300 may be formed between the first substrate100 and the second substrate 200. When the first and second alignmentlayers 180 and 280 are formed by the UV alignment process, the liquidcrystal layer 300 may be formed of negative liquid crystal, but is notlimited thereto. The negative liquid crystal is liquid crystal of whichdielectric anisotropy (Δε=ε//−ε⊥) is a negative (−) value. The negativeliquid crystal is more effective than positive liquid crystal, which isliquid crystal of which dielectric anisotropy has a positive (+) value,in terms of a transmittance or luminance.

The sealant 400 may be formed between the first substrate 100 and thesecond substrate 200. The sealant 400 may be formed in an edge area ofeach of the first substrate 100 and the second substrate 200 to bond thefirst substrate 100 to the second substrate 200. The sealant 400 maycontact at least one of the first and second alignment layers 180 and280, and particularly, may be chemically bonded to an alignment layercontacting the sealant 400. Although it is illustrated in the drawingthat the sealant 400 contacts all the first and second alignment layers180 and 280, the sealant 400 may create a chemical bond in contact withone of the first and second alignment layers 180 and 280.

The sealant 400 may include the diene compound represented by ChemicalFormula 1 which is capable of being chemically bonded to the maleimidefunctional group, included in the first and second alignment layers 180and 280, by UV rays which are irradiated when hardening the sealant 400.Therefore, a contact surface between the sealant 400 and the firstalignment layer 180 or a contact surface between the sealant 400 and thesecond alignment layer 280 may include the compound represented byChemical Formula 3 created by Reaction Formula 1.

In this case, since each of the first and second alignment layers 180and 280 has a predetermined alignment direction, the alignment directionof each of the first and second alignment layers 180 and 280 may not bechanged by the UV rays which are irradiated when hardening the sealant400.

That is, a chemical bond of a compound for each of the first and secondalignment layers 180 and 280 may not be broken within a wavelength rangeof the UV rays which is irradiated when hardening the sealant 400. Inother words, an alignment direction of the compound for each of thefirst and second alignment layers 180 and 280 may be determined by UVrays having a wavelength range which does not overlap the wavelengthrange of the UV rays which is irradiated when hardening the sealant 400.

The sealant 400 may include an epoxy resin capable of being chemicallybonded to a COOH group of amic acid included in each of the first andsecond alignment layers 180 and 280. Therefore, the contact surfacebetween the sealant 400 and the first alignment layer 180 or the contactsurface between the sealant 400 and the second alignment layer 280 mayinclude a COO bond by a reaction of an epoxy resin with a COOH group.However, when the first and second alignment layers 180 and 280 areformed by the UV alignment process, the epoxy resin may not be includedin the sealant 400.

The sealant 400 may include an acryl resin, a polymerization initiator,a coupling agent, a hardener, and a filler, in addition to the dienecompound represented by Chemical Formula 1 and the epoxy resin.

The polymerization initiator may include an UV initiator and a heatinitiator. The UV initiator and the heat initiator may use variousmaterials known to those skilled in the art. The coupling agent may usea silane-based compound, but is not limited thereto. As another example,the coupling agent may use various materials known to those skilled inthe art. The hardener may also use various materials known to thoseskilled in the art. The filler may include a silica component, but isnot limited thereto. As another example, the filler may use variousmaterials known to those skilled in the art.

In the drawing, the sealant 400 is illustrated as contacting theovercoat layer 160 on the first substrate 100 and the planarizationlayer 240 on the second substrate 200, but is not limited thereto. Forexample, the overcoat layer 160 may not extend to the edge area of thefirst substrate 100, and thus, the sealant 400 may contact the lightshielding pattern 120 on the first substrate 100. Also, theplanarization layer 240 may not extend to the edge area of the secondsubstrate 200, and thus, the sealant 400 may contact the passivationlayer 230.

It is illustrated in the drawing that only a portion of the sealant 400contacts the first and second alignment layers 180 and 280, but a wholeportion of the sealant 400 may contact the first and second alignmentlayers 180 and 280.

As described above, according to the embodiment of the presentinvention, since the sealant includes a diene compound, the dienecompound may be chemically bonded to the alignment layer, therebyenhancing a bonding force between the sealant and the alignment layer.Accordingly, an adhesive force between the first substrate and thesecond substrate is enhanced.

Moreover, according to the embodiment of the present invention, sincethe sealant and the alignment layer are formed to contact each other, abezel width of a device apparatus is reduced, thereby providing thedisplay apparatus where a display screen displaying an image isenlarged.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the inventions. Thus, itis intended that the present invention covers the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

What is claimed is:
 1. A liquid crystal display (LCD) device,comprising: a first substrate and a second substrate facing each other;a liquid crystal layer between the first substrate and the secondsubstrate; an alignment layer on at least one of the first substrate andthe second substrate for alignment of liquid crystals in the liquidcrystal layer, the alignment layer including a maleimide functionalgroup; and a sealant in an edge area of each of the first substrate andthe second substrate to bond the first substrate to the secondsubstrate, the sealant including a diene compound, wherein the sealantcontacts the alignment layer to chemically bond the diene compound tothe maleimide functional group of the alignment layer, and wherein thediene compound is represented by Chemical Formula 1:

where R₁, R₂, and R₃ are independently one among hydrogen, a halogenatom, a phenyl group, an alkyl group of C₁˜C₉, an alkoxy group of C₁˜C₉,a vinyl group of C₂˜C₄, and an acetyl group of C₂˜C₄, and R₄ is oneamong a phenyl group, an alkyl group of C₁˜C₉, an alkoxy group of C₁˜C₉,a vinyl group of C₂˜C₄, and an acetyl group of C₂˜C₄.
 2. The LCD deviceof claim 1, wherein the alignment layer comprises a compound representedby Chemical Formula 2:

where R₅ is one among hydrogen, a halogen atom, a phenyl group, an alkylgroup of C₁˜C₉, an alkoxy group of C₁˜C₉, a vinyl group of C₂˜C₄, and anacetyl group of C₂˜C₄, and R₆ and R₇ are independently one amonghydrogen and an alkyl group of C₁˜C₆.
 3. The LCD device of claim 1,wherein a contact surface between the sealant and the alignment layercomprises a compound represented by Chemical Formula 3:

where R₁, R₂, R₃, and R₅ are independently one among hydrogen, a halogenatom, a phenyl group, an alkyl group of C₁˜C₉, an alkoxy group of C₁˜C₉,a vinyl group of C₂˜C₄, and an acetyl group of C₂˜C₄, and R₄ is oneamong a phenyl group, an alkyl group of C₁˜C₉, an alkoxy group of C₁˜C₉,a vinyl group of C₂˜C₄, and an acetyl group of C₂˜C₄, and R₆ and R₇ areindependently one among hydrogen and an alkyl group of C₁˜C₆.
 4. The LCDdevice of claim 1, wherein the diene compound is chemically bonded tothe alignment layer by ultraviolet (UV) rays.
 5. The LCD device of claim4, wherein a chemical bond of a compound for the alignment layer is notbroken within a wavelength range of the UV rays.
 6. The LCD device ofclaim 5, wherein the wavelength range of the UV rays includes 300 nm to420 nm.
 7. The LCD device of claim 4, wherein an alignment direction ofa compound for the alignment layer is determined by UV rays having awavelength range which does not overlap with a wavelength range of theUV rays involved in the diene compound chemically bonding to thealignment layer.
 8. The display apparatus of claim 7, wherein thewavelength range of the UV rays determining the alignment direction ofthe compound for the alignment layer includes 240 nm to 254 nm.
 9. TheLCD device of claim 1, wherein the sealant further includes an epoxyresin, and the alignment layer includes amic acid.
 10. The LCD device ofclaim 9, wherein a contact surface between the sealant and the alignmentlayer includes a COO bond by a reaction of the epoxy resin with acarboxylic group (COOH) of the amic acid.
 11. A liquid crystal display(LCD) device, comprising: a first substrate and a second substratefacing each other; a liquid crystal layer between the first substrateand the second substrate; an alignment layer on at least one of thefirst substrate and the second substrate for alignment of liquidcrystals in the liquid crystal layer, the alignment layer including amaleimide functional group; and a sealant in an edge area of each of thefirst substrate and the second substrate to bond the first substrate tothe second substrate, the sealant including a diene compound, andwherein the sealant contacts the alignment layer to chemically bond thediene compound to the maleimide functional group of the alignment layer,wherein a contact surface between the sealant and the alignment layercomprises a compound represented by Chemical Formula 1:

where R₁, R₂, R₃, and R₅ are independently one among hydrogen, a halogenatom, a phenyl group, an alkyl group of C₁˜C₉, an alkoxy group of C₁˜C₉,a vinyl group of C₂˜C₄, and an acetyl group of C₂˜C₄, and R₄ is oneamong a phenyl group, an alkyl group of C₁˜C₉, an alkoxy group of C₁˜C₉,a vinyl group of C₂˜C₄, and an acetyl group of C₂˜C₄, and R₆ and R₇ areindependently one among hydrogen and an alkyl group of C₁˜C₆.
 12. TheLCD device of claim 11, wherein the diene compound comprises a compoundrepresented by Chemical Formula 2:

where R₁, R₂, and R₃ are independently one among hydrogen, a halogenatom, a phenyl group, an alkyl group of C₁˜C₉, an alkoxy group of C₁˜C₉,a vinyl group of C₂˜C₄, and an acetyl group of C₂˜C₄, and R₄ is oneamong a phenyl group, an alkyl group of C₁˜C₉, an alkoxy group of C₁˜C₉,a vinyl group of C₂˜C₄, and an acetyl group of C₂˜C₄.
 13. The LCD deviceof claim 11, wherein the alignment layer comprises a compoundrepresented by Chemical Formula 2:

where R₅ is one among hydrogen, a halogen atom, a phenyl group, an alkylgroup of C₁˜C₉, an alkoxy group of C₁˜C₉, a vinyl group of C₂˜C₄, and anacetyl group of C₂˜C₄, and R₆ and R₇ are independently one amonghydrogen and an alkyl group of C₁˜C₆.
 14. The LCD device of claim 11,wherein the diene compound is chemically bonded to the alignment layerby ultraviolet (UV) rays.
 15. The LCD device of claim 14, wherein achemical bond of a compound for the alignment layer is not broken withina wavelength range of the UV rays.
 16. The LCD device of claim 15,wherein the wavelength range of the UV rays includes 300 nm to 420 nm.17. The LCD device of claim 14, wherein an alignment direction of acompound for the alignment layer is determined by UV rays having awavelength range which does not overlap with a wavelength range of theUV rays involved in the diene compound chemically bonding to thealignment layer.
 18. The display apparatus of claim 17, wherein thewavelength range of the UV rays determining the alignment direction ofthe compound for the alignment layer includes 240 nm to 254 nm.
 19. TheLCD device of claim 11, wherein the sealant further includes an epoxyresin, and the alignment layer includes amic acid.
 20. The LCD device ofclaim 19, wherein a contact surface between the sealant and thealignment layer includes a COO bond by a reaction of the epoxy resinwith a carboxylic group (COOH) of the amic acid.